IEEE Standards Interpretation for IEEE Std 1003.1™-2001 IEEE Standard Standard for Information Technology -- Portable Operating System Interface (POSIX®)
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Interpretation Request #50
Topic: XBD errno.h Relevant Sections: XBD errno.h Page: 219 Line: 7166
POSIX requires that the symbolic constants for error codes are unique, except as marked. In the list, EWOULDBLOCK is permitted to have the same value as EAGAIN.
However, ENOTSUP (line 7777) and EOPNOTSUPP (line 7780) are not permitted to have the same value. No interface is defined that could return either code, and many implementations exist where these two symbols DO have the same value (and are therefore currently non-conforming).
On p 221, line 7777, change [ENOTSUP] Not supported to [ENOTSUP] Not supported (may be the same value as [EOPNOTSUPP]) and at line 7780, change [EOPNOTSUPP] Operation not supported on socket to [EOPNOTSUPP] Operation not supported on socket (may be the same value as [ENOTSUP]).
Interpretation Response #50
The standard is clear, and conforming implementations must provide these symbols with distinct values. Concerns have been raised and are being forwarded to the sponsor.
Rationale for Interpretation